What Is "Seeing" in Astrophotography? The Science Behind Atmospheric Turbulence
7 comments
·June 3, 2025gattr
dylan604
I've been out in very poor seeing conditions, and it is just miserable. I was only doing wide angle and not using a scope, but the sky was so turbulent that I couldn't get proper focus. For those of us in the northern hemisphere, the best time for imaging the center of the milky way lines up with summer. Summer is just horrible seeing conditions in my area with >100° temps deep into the night with high humidity levels. Every now and then a new moon lines up with a nice thunderstorm which clears out the air and brings down the temps. Anyone want to take bets on the over/under of how often that happens?!
barbazoo
> Excellent comparison! Thx for sharing :-)
> No problem! For all those occasions when laypeople ask about your imaging and the importance of seeing comes up.
> 26 Jul 2016
Love that this resource has been kept alive for almost 10 years now serving its very purpose.
karlperera
Just read up about the airy disk. That's quite interesting. Seeing can be such a complicated subject and so much maths is involved in astronomy. When I deal with the subject, I always try to simplify things and get away from the maths. For astrophotographers such as myself I believe we shouldn't dwell too much on all the unknowns we cannot control and I generally stay away from the maths. I'm more interested in the practicalities of improving the quality of the image with the conditions as they are.
karlperera
Most people think better telescopes or cameras are the key to sharper astrophotography, but there’s a hidden culprit that often matters more: “seeing.” I always wondered why, on some nights, even the best gear produced blurry, shimmering images—especially of planets and the Moon. It turns out the real limit is the turbulence in Earth’s atmosphere, which bends and distorts light in unpredictable ways.
In this post, I break down what “seeing” actually means, how it’s measured (arcseconds!), and why even perfect-looking nights can ruin your images. I also share some surprising lessons I learned about how geography, altitude, and even the time of night can make or break your results. If you’ve ever been frustrated by fuzzy details or want to understand the real physics behind the “twinkle” of stars, I’d love to hear your experiences and tips.
Let’s discuss: How do you deal with seeing, and have you found any tricks that actually work?
barbazoo
> Most people think better telescopes or cameras are the key to sharper astrophotography, but there’s a hidden culprit that often matters more: “seeing.” I always wondered why, on some nights, even the best gear produced blurry, shimmering images—especially of planets and the Moon. It turns out the real limit is the turbulence in Earth’s atmosphere, which bends and distorts light in unpredictable ways. In this post, I break down what “seeing” actually means, how it’s measured (arcseconds!), and why even perfect-looking nights can ruin your images. I also share some surprising lessons I learned about how geography, altitude, and even the time of night can make or break your results. If you’ve ever been frustrated by fuzzy details or want to understand the real physics behind the “twinkle” of stars, I’d love to hear your experiences and tips.
> Let’s discuss: How do you deal with seeing, and have you found any tricks that actually work?
Reads AI generated to me. https://gptzero.me/ agrees.
AStonesThrow
I've been using The Clear Sky Chart to predict cloudy conditions. There is an hourly "Seeing" rating corresponding to the cloud-cover forecasts.
Here's a comparison of bad and good seeing (captured with a D = 90 mm telescope with a solar Hα filter):
https://app.astrobin.com/u/GreatAttractor?i=246828#gallery
Technically speaking, in the first half of the vid the incoming wavefronts are distorted (the Fried parameter r₀ is smaller than the telescope's diameter D) and do not focus to a clean, tight Airy pattern ([1]). In the second half, r₀ is above D and we're left with just some rubber-membrane distortion (the wavefronts are tilted this way and that, but remain mostly planar), which can be corrected in software.
[1] https://en.wikipedia.org/wiki/Airy_disk